1. Field of the Invention
The present invention relates to an infrared light irradiation lamp for an automobile which is mounted on an automobile and illuminates a forward portion of a vehicle with an infrared light, and more particularly to an infrared light irradiation lamp for an automobile which has such a structure that an infrared light is formed by a globe for infrared light formation covering a bulb to be a light source and which is shared with a CCD camera having a sensitivity up to a near-infrared.
2. Description of the Related Art
For example, this kind of lamp has such a structure that a visible light source and a reflector are provided in a lighting chamber formed by a lamp body and a front lens, an infrared light transmission globe having a surface coated with an infrared light transmission multilayer film is provided to cover the visible light source, and an infrared light in a light source light which is transmitted through a globe is reflected by the reflector, is transmitted through the front lens and is distributed forward.
An image of an infrared light irradiation region in a forward portion of a vehicle is captured by a CCD camera having a sensitivity up to a near-infrared provided in a front part of an automobile, is processed by an image processing apparatus and is projected onto a monitor screen in a vehicle compartment. A driver can confirm a person, a lane mark and an obstacle over the monitor screen projecting a field of view in the forward part of the vehicle at a great distance.
Moreover, the applicant has proposed, in JP-A-2000-36885, a lamp capable of being alternatively selected into an infrared light irradiation lamp and a headlamp (a main beam irradiation lamp) by switching a configuration (an infrared light irradiation configuration) in which an infrared light transmission globe provided in such a position as to cover a visible light source is movably constituted in an axial direction and the globe is positioned to cover the visible light source so that an infrared light is irradiated, and a configuration (a visible light irradiation configuration, a main beam irradiation configuration of the headlamp) in which the globe is moved forward from the visible light source so that a portion provided around the visible light is released and the visible light is thereby irradiated.
In the JP-A-2000-36885, however, when the lamp is to be used as the infrared light irradiation lamp, a tungsten halogen bulb to be a visible light source is surrounded by the infrared light transmission globe. Therefore, the inside of the globe is filled with heat generated from the bulb so that the inside of the globe has a high temperature. For this reason, there is a problem in that the halogen cycle of the tungsten halogen bulb does not function so that the lifetime of the bulb or the infrared light transmission globe is shortened, for example, blacking is generated to decrease an amount of a light or the infrared light transmission multilayer film of the globe is deteriorated to reduce an infrared cut characteristic.
The invention has been made in consideration of the problems of the prior art and has an object to provide an infrared light irradiation lamp in which the inside of a globe for infrared light formation at time of infrared light irradiation does not have such a high temperature that the infrared ray transmission characteristic of the globe and the lifetime of a bulb are not adversely influenced.
In order to achieve the object, a first aspect of the invention is directed to an infrared light irradiation lamp for an automobile comprising a lighting chamber formed by a lamp body and a front lens, a reflector provided in the lamp body, a light source provided ahead of the reflector, a cylindrical globe for infrared light formation provided to cover the light source and serving to shield a visible light and to transmit only an infrared light and a globe moving mechanism for moving the globe, the globe moving mechanism being capable of switching a lamp function into an infrared light irradiation configuration in which the globe for infrared light formation covers the light source and a visible light irradiation configuration in which the globe for infrared light formation is moved forward from the light source,
wherein power regulating means is provided on a power supply path reaching the light source and a power supplied from the light source in the infrared light irradiation configuration is regulated to be lower than a power supplied from the light source in the visible light irradiation configuration.
In the visible light irradiation configuration, the globe for infrared light formation is provided ahead of the light source and a portion provided around the light source is released. Therefore, there is no possibility that the heat generated from the light source might be radiated into the space of the lighting chamber which is provided around the light source and the globe and the light source themselves might be exposed to a high temperature. On the other hand, in the infrared light irradiation configuration, the globe for infrared light formation is positioned to cover the light source so that the inside of the globe is apt to be filled with the heat generated from the light source. However, since the power regulated by the power regulating means (which is lower than the power to be supplied to the light source in the visible light irradiation configuration) is supplied to the light source, the amount of heat generation in the light source is correspondingly reduced so that the inside of the globe can be prevented from having a high temperature. More specifically, the temperature in the globe does not have such a high temperature that the visible light cut and infrared ray transmission characteristic of the globe and the lifetime of the light source are influenced adversely.
Moreover, it is desirable that the power regulating means should be operated in connection with the switching of the lamp function by the globe moving mechanism. By such a structure, it is not necessary to operate the power regulating means manually.
The light distribution of the lamp includes the case in which a step for light distribution control is not provided on the front lens but the light is controlled and formed by only the reflector in addition to the case in which the light reflected by the reflector is controlled and formed at the step for light distribution control provided on the front lens. It is assumed that the front lens also includes the front lens having no step for light distribution control, that is, a so-called front cover.
A second aspect of the invention is directed to the infrared light irradiation lamp for an automobile according to the first aspect of the invention, wherein a source voltage is directly supplied to the light source in the case in which the power regulating means is not operated and the power regulating means has the lamp function in the infrared light irradiation configuration and drops the power supplied from the light source when the source voltage exceeds a predetermined value.
In the visible light irradiation configuration in which the portion provided around the light source is released so that the globe for infrared light formation and the light source themselves are not exposed to a high temperature, a power having an exact source voltage is supplied to form a main beam in a sufficient amount of a light. On the other hand, in the infrared light irradiation configuration in which there is a possibility that the inside of the globe might be filled with heat to expose the globe and the light source themselves to a high temperature, the amount of heat generation of the light source is not greatly increased if the source voltage does not exceed a predetermined value (for example, 12V). In the same manner as the case of the visible light irradiation configuration, therefore, a power having an exact source voltage is supplied to the light source to form an infrared beam in a sufficient amount of a light. Consequently, the detection of a night forward field-of-view detecting system using a CCD camera can easily be carried out. If the source voltage exceeds the predetermined value (for example, 12V), a power (for example, a power of 12V) regulated by the power regulating means is supplied to the light source such that the amount of heat generation in the light source is not increased. Thus, a temperature in the globe can be prevented from being increased.
A third aspect of the invention is directed to the infrared light irradiation lamp for an automobile according to the first or second aspect of the invention, wherein the globe for infrared light formation in the infrared light irradiation configuration has a rear end provided apart from the reflector.
In the infrared light irradiation configuration, an air convection is generated across the inside and outside of the globe for infrared light formation through a clearance provided between the reflector and the rear end of the globe for infrared light formation. Thus, the heat in the globe is radiated out of the globe.
With such a structure that a light source holding member (a bulb holder) formed of metal which has an extended portion extended into the globe for infrared light formation and a radiation fin extended to the back of the reflector is provided between the light source attachment hole (bulb insertion hole) of the reflector and the mouth piece of the light source (bulb), moreover, heat generated by turning on the light source is transmitted to the light source holding member so that the heat is radiated from the radiation fin into the space provided on the back of the reflector (for example, in the lighting chamber) and the globe for infrared light formation is not thereby filled with the heat.